Superconducting MgB2 Thin Film Detector for Neutrons

The superconducting neutron detector using high-quality ¹⁰B-enriched MgB₂ thin films at higher operating temperatures has been proposed, where a resistance change induced by the nuclear reaction of neutron and ¹⁰B in MgB₂ is used to detect a neutron. Cold neutrons from a nuclear research reactor irradiated the MgB₂ detector, and the output voltage was clearly observed through a low-noise amplifier by using a digital oscilloscope. The out-of-equilibrium thermodynamics was investigated by means of the time-dependent Ginzburg-Landau equations by using the Earth Simulator.      

Effect of Carrier Frequency and Circuit Resistance on Iron Loss of Non‐Oriented Electrical Steel Sheet under Single‐Phase Full‐Bridge PWM Inverter Excitation

Because of the development of power electronics technology, pulse width modulation (PWM) inverters are now being used to drive motors in order to achieve precise and energy‐efficient control. Precise estimation of the increase in iron loss due to the high harmonic components of flux, including the carrier frequency, is important in the design of motors excited by a PWM inverter. We measured the iron losses of non‐oriented electrical steel sheets that were excited using a single‐phase full‐bridge PWM inverter, and examined the influence of the carrier frequency and circuit resistance on the iron loss. We showed that the iron loss increased because of the generation of minor loops when the circuit resistance was high. Therefore, the circuit resistance should be decreased in an actual motor system.     

Mesoporous Material from Zeolite

Zeolite/mesoporous molecular sieve composites (ZMC) are made using zeolites as silica-alumina source. XRD patterns of the ZMC show the peaks for both zeolite and mesoporous molecular sieve with hexagonal symmetry. Morphology of the ZMC is different from that of a physical mixture of the two components. Unlike Al-containing mesoporous molecular sieves, the ZMC shows a strong acidity like zeolites. The activity of cracking of n-hexane for ZMC was higher than that of the zeolite. These products are expected to be useful for catalysts and adsorbents for their acidity and pore size.     

Capacitive voltage sensor for measuring very fast transient overvoltages in GIS

A reliable technique is needed for accurate measurement of very fast transient overvoltages such as disconnector-induced surges occurring in GIS which have very steep front and high-frequency oscillation. Recently, capacitive voltage sensors with very short response times have been proposed for this purpose. However, few studies have been made on the dielectric properties of materials used for a low-voltage-side capacitor, as well as the frequency bandwidth of the measuring system. In this paper a thin mica plate is proposed for a low-voltage-side capacitor which has a surface coated with silver on both sides. This material has been shown to have stable and high static capacitance up to a high-frequency range. A quantitative estimate also is given for the frequency bandwidth of the measuring system. Furthermore, a practical-scale sensor of this type has been developed which can successfully measure simulated disconnector-induced surges of several hundred kilovolts under similar conditions in GIS.     

Highly strained ln0.35Ga0.65As/GaAs layers grown by molecular beam epitaxy for high hole mobility transistors

We have grown highly strained In_0.35Ga_0.65As layers on GaAs substrates by molecular beam epitaxy to improve the performance of high hole mobility transistors (HHMTs). The mobility and sheet hole concentration of double side doped pseudomorphic HHMT structures at room temperature reached 314 cm2/V-s and 1.19 × 10¹² cm⁻², respectively. Photoluminescence measurements at room temperature show good crystalline quality of the In^0.35Ga_0.65As layers. This study suggests that the performance of HHMTs can be improved by using high-quality In_0.35Ga_0.65As layers for the channel of double side doped heterostructures pseudomorphically grown on GaAs substrates.     

Fe-Promoted selective methanol synthesis in CO hydrogenation catalyzed on SiO2-supported Ir4Fe and Pd6Fe6 bimetallic carbonyl cluster-derived catalysts

The bimetallic catalysts prepared from Ir₄Fe and Pd₆Fe₆ carbonyl clusters exhibited high activities and selectivities towards methanol from CO + H₂. In contrast, hydrocarbons and CO₂ were preferentially obtained on the catalyst prepared from Fe-rich PdFe₄ cluster. The promotion towards methanol synthesis on the SiO₂-supported Ir₄Fe and Pd₆Fe₆ cluster catalysts was proposed to be associated with Pd-Fe³⁺ and Ir-Fe³⁺ sites located at the metal-support interface.